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Land snail diversity and composition in relation to ecological variations in Central European floodplain forests and their history
Abstract
We explored patterns of land snail assemblages using 93 alluvial forest sites in six river floodplains of the Elbe drainage basin (northwestern Bohemia, Czech Republic). Differences in species richness and composition across the four floodplain forest types (i.e., alder carrs, ash-alder forests, willow-poplar softwood forests, and hardwood forests) were analysed using generalized linear models, multidimensional scaling and redundancy analysis with the Monte Carlo permutation test. The studied floodplain forest types did not differ in species richness, except for the alder carrs which were significantly poorer. The number of species expressed a significant unimodal response along with elevation and Ellenberg nutrients, and further significantly decreased towards the most humid sites. Contrary to species richness, the main forest types clearly differed based on land snail species composition, with the exception of the ash-alder and willow-poplar forest sites which became completely overlapped in the ordination space. The main changes in species composition were mostly associated with elevation and Ellenberg moisture on the first MDS axis: Ellenberg nutrients and light were fitted on the second and the third axes, respectively. These variables, along with calcium content estimated using Ellenberg indicator values for soil reaction, had significant effects on the variation and snail species composition in the final RDA model. No response of either species richness or compositional changes was found for the measured content of topsoil calcium, most likely due to the higher importance of other variables. On the basis of some recently published data we can conclude that historical development and long-term human activities on the succession of floodplain assemblages have resulted in a sharp impoverishment of strictly land snail species of several hardwood forest sites in the majority of lower river stretches. Whilst in most areas there are no exact palaeoecological data available, these historical influences were closely correlated with the site elevation in our dataset as the main difference in species composition was hard to explain solely using environmental predictors.
... The numbers of each taxon were determined in the samples. Individual species of molluscs were included into ecological groups according to the scheme developed by Ložek (1964), Alexandrowicz (2011) andJuřičková et al. (2014). The data compiled this way was used to construct the malacological spectrum of individuals (MSI). ...
... Transport and deposition of shell material during the flood was described by several authors (e.g. Pip, 1988;Briggs et al., 1990;Cummins, 1994;Moulthon, 1999;Foeckler et al., 1991Foeckler et al., , 2006Ilg et al., 2009Ilg et al., , 2012Jurkiewicz-Karnkowska, 2009;Poiriera et al., 2010;Alexandrowicz & Alexandrowicz, 2011;Horáčková et al., 2014Horáčková et al., , 2015Čiliak et al., 2015). The most of such analyses were focused on valleys of Table 1 and Fig. 3, 1-32 -research sites large rivers, while the significantly smaller attention attaching to smaller streams. ...
... Pišút & Čejka, 2002;Horsák et al., 2009;Alexandrowicz, 2010). Studies of shell offsets also provide important information about the variability, diversity and characteristics of malacocoenosis inhabiting floodplains and their relationship with short-term environmental changes, often resulting from human activity (Alexandrowicz, 2002;Horáčková et al., 2014Horáčková et al., , 2015. An important aspect of the analysis of thanatocenosis is the ability to assess the degree of similarity of their composition and ecological structure to living malacocoenosis inhabiting a given area. ...
... Abbreviations of taxa names are given in Table 3 1828)), as well as some rare polyhygric species (e.g., Vallonia enniensis (Gredler, 1856) and Vertigo moulinsiana (Dupuy, 1849)) in the monitored floodplain area. Over the last 50 years, a number of studies dealing with molluscan fauna have been published from the floodplains of European rivers (e.g., Frank 1984;Obrdlík et al. 1995;Horsák 2000;Ilg et al. 2009;Horáčková et al. 2014). ...
... Most of these studies is only descriptive, without any findings of the key environmental drivers explaining the current state of diversity and taxonomical composition of the molluscan fauna. Soil moisture is one of the most important environmental factors that affect the local diversity of soil fauna (Silvan et al. 2000;Morecroft et al. 2002) and has often been considered as the key determinant responsible for the differences in taxonomical and functional richness of land snail assemblages between alluvial habitats (Wäreborn 1969;Gleich and Gilbert 1976;Wardhaugh 1995;Martin and Sommer 2004;Horáčková et al. 2014). Some of the previous studies documented a significant response of land snail diversity to the change in soil moisture, i.e., increasing species richness in wetter habitats (Wäreborn, 1969;Martin and Sommer 2004). ...
... Some of the previous studies documented a significant response of land snail diversity to the change in soil moisture, i.e., increasing species richness in wetter habitats (Wäreborn, 1969;Martin and Sommer 2004). Despite several adaptations to habitat drying (e.g., estivation in the shell, production of temporary epiphragma, or mechanical burrowing into the top layers of soil), most species preferred a certain range of soil moisture (Čejka and Hamerlík 2009;Horáčková et al. 2014). However, it appears that this relationship is habitat-specific and probably relates also to synergic effects of soil moisture with other environmental variables important for snails as well, such as vegetation type, soil pH, and calcium content in topsoil. ...
The Gabčíkovo Water Project, a major construction of damming and canalizing on the upper part of the middle Danube, significantly changed hydrological regime of the Danube inland delta, destroyed or affected most of the 230 km² of wetlands and directly disrupted the original and unique ecosystem along a 37 km long river stretch. The aim of this study was to describe the effect of the Gabčíkovo Waterworks on the taxonomical and functional structure of the molluscan assemblages in the Danube riparian floodplain forests. The results demonstrate that the Gabčíkovo Waterworks had a direct and long-lasting effect on the direction of the succession of terrestrial molluscan assemblages, especially in the area of the by-pass section. The changes in the soil moisture caused by the waterworks’ operation led to significant changes in the species and functional composition of these assemblages. More specifically, however, the proportion of the generalists which prefer dry biotopes increased, while the number of moisture-demanding species decreased. Our results indicate that the current artificial flooding system cannot fully replace previous natural floods in the Danube inland delta, and it is also insufficient for restoration and preservation of the humidity conditions in the softwood floodplain forests which would be similar to the pre-operation period of the Gabčíkovo Waterworks.
... Elevation, depth of leaf litter and the presence of dead wood were the most important environmental variables affecting the occurrence patterns of the snail species and the assemblage composition in the gallery forests (Table 1). Elevation and nutrients (corresponding to leaf litter) were also found to shape the species composition of land-snail assemblages in floodplain forests in the Elbe drainage basin in the Czech Republic (Horáčková, Horsák & Juřičková, 2014). Horáčková et al. (2014) also identified light conditions as an important parameter influencing species composition, whereas canopy cover (determining the light that reaches the forest floor) had no significant impact on the composition of the snail assemblages in the Muvumba valley. ...
... Elevation and nutrients (corresponding to leaf litter) were also found to shape the species composition of land-snail assemblages in floodplain forests in the Elbe drainage basin in the Czech Republic (Horáčková, Horsák & Juřičková, 2014). Horáčková et al. (2014) also identified light conditions as an important parameter influencing species composition, whereas canopy cover (determining the light that reaches the forest floor) had no significant impact on the composition of the snail assemblages in the Muvumba valley. ...
... Land-snail species richness in the studied gallery forest along the Muvumba River increased significantly with elevation (Table 1). An increase of species richness of land-snail assemblages in floodplain forests with elevation was also observed in the Elbe drainage basin in the Czech Republic (Horáčková et al., 2014). Since the elevation of the sampled plots in the Muvumba valley varied only between 1,330 and 1,360 m above sea level, elevation is certainly not a proxy for climate in this case. ...
We investigated the land-snail fauna in gallery forest sites along a 30-km long section of the Muvumba River in northeastern Rwanda. A total of 12,419 individuals assigned to 34 land-snail species were collected in 24 plots. Though the number of species is small compared with protected rainforests in the northern Albertine Rift, gallery forests are important as corridors for colonization for the forest fauna. Despite a strong human impact on the gallery forests, hardly any obviously introduced species were recorded. The composition of the snail assemblages was significantly affected by elevation, depth of leaf litter and the presence of dead wood. The high median abundances of the snails in the gallery forests, which are among the highest recorded from forests in the northern Albertine Rift, are probably the result of a higher average soil calcium content in these gallery forests, caused by flooding. The significant increase of land-snail species richness with elevation might be the result of a higher input of calcium into the upper part of the study area.
... Mollusc communities vary among forests of different inundation frequency (e.g. körnig 1966, kerkHoff 1989, Horáčková et al. 2014, and have been suggested as indicators of duration of inundation episodes (e.g. follner & Henle 2006). ...
... Habitat changes in floodplains bring about impoverishment of gastropod communities (e.g. Horáčková et al. 2014). Already steusloff (1950) noted that suitable habitats for snail groups such as door snails had almost completely disappeared in the hostile matrix of the anthropogenic agricultural steppe on the Lower Rhine. ...
... Martin & soMMer 2004, čejka et al. 2008, čejka & Hamerlík 2009, kappes & scHiltHuizen 2014, as does inundation (e.g. kerkHoff 1989, Horáčková et al. 2014. The soils of the forests along the Rhine River are usually dry, among others because the ground water level has decreased along with the level of the river. ...
The Rhine floodplain is much modified by human land use. What used to be the hardwood zone of the large floodplain nowadays holds only a few isolated, recent (mostly < 60 years) forest patches. The aim of the study was to check if the circumstances favoured homogeneity of the snail communities, usually observed within floodplains, or if heterogeneity prevailed. We inventoried molluscs (presence-absence) in 21 sites within and 18 sites adjacent to a stretch of the Lower Rhine floodplain (total 39 sites). Communities from eight of the sites were quantitatively sampled for within-site analyses. Species turnover occurred with distance from the Rhine, partially along with lateral habitat turnover. Introduced species mainly occurred in young forests, in similar numbers within and beyond the floodplain. Old forests beyond the floodplain had a small number of introduced species and a small between-site heterogeneity, suggesting strong habitat filters (selection of species by environmental conditions) which might be associated with the prevalence of detritus-derived food. The occasionally flooded sites had the longest scatter along the first NMDS axis, indicating a local differentiation without a longitudinal gradient. The young forests that were occasionally inundated and those that were never flooded shared many species, resulting in the lack of significant differences based on the presence-absence data. The damp, regularly flooded forests differed from the occasionally inundated ones and the ones beyond the floodplain. Flooding introduces drift material and species to the sites. The drift is associated with an initially increased within-site heterogeneity. During the years after the flooding event, the within-site homogeneity of communities increases (suggesting local selection of species) in tandem with an increase in the between-site differences (local selection plus stochastic extinctions).
... However until now, the fauna of alluvial forests was neglected. Studies on the floodplain forests of the Danube River (Čejka et al., 2008) and the Elbe River including its tributaries (Horáčková et al., 2014b) were published in the last couple of years. ...
... As an example can serve the Myslivna Nature Reserve on the Ohře River protected as an original natural old floodplain forest. However, based on fossil mollusc succession and composition of recent malacocoenoses that are missing mainly woodland species of gastropods (Horáčková et al., 2014b) we consider this protected floodplain forest as relatively recent. While there are recently living many woodland snail species in the upper stretches of the Ohře River, almost half of them are missing in the lower stream of the river despite the fact that there are large protected woodland complexes of floodplain forests offering seemingly ideal habitat for the woodland snails. ...
... The composition and the species diversity of the floodplain snail assemblages are related mainly to altitude and moisture gradients (Horáčková et al., 2014b). The influence of altitude on mollusc assemblages has been described many times and is obviously related to winter temperatures (e.g. ...
River floodplains of Czech rivers serve as refugia to woodland or hydrophilous gastropods, in current intensively agriculturally utilised, urbanised and largely fragmented landscape. This habitat often form one of the last refuge and replace the natural habitat of these species. River floodplains also represent linear bio-corridors in landscape and allow gastropods to spread through the landscape in both directions, up and down the stream. We showed based on available fossil mollusc successions that development of the floodplain mollusc fauna took place quite different way in various river floodplains, depending on their specifics and geographical location, because especially the ones situated in the chernozem area of the Czech Republic had very different history in comparison with those in higher altitudes. The species richness and composition of recent floodplain malacofauna arises from historical development of particular area/site and depends also on environmental factors such as an elevation, humidity gradient, vegetation type and its biomass, light conditions of the site and soil reaction. Recently, the invasive plants represent a serious problem for current floodplain ecosystems; species richness and abundances of terrestrial mollusc floodplain assemblages are changing due to their effect. The impact on gastropods is species-specific and was described for the following species:
... Some studies have suggested that land snails may be useful as ecological indicator species in terms of their response to environmental changes (Douglas et al., 2013;Gheoca et al., 2021). Studies of community ecology using land snails have revealed that community composition and species diversity are determined by a variety of biotic and abiotic factors along elevation gradients (Aubry et al., 2005;Baur et al., 2014;Dvořáková and Horsák, 2012;Horáčková et al., 2014;Tattersfield et al., 2006). Additionally, due to intercorrelations among its environmental variables via elevation, it is often difficult to determine which environmental factors directly affect land snail communities (Dvořáková and Horsák, 2012;Labaune and Magnin, 2001). ...
... Previous studies focusing on land snail communities have shown that community composition and species diversity vary along elevational gradients (Aubry et al., 2005;Baur et al., 2014;Dvořáková and Horsák, 2012;Horáčková et al., 2014;Tattersfield et al., 2006). However, since elevation is correlated with multiple environmental variables, it has been difficult to identify environmental variables that have direct effects on community (Dvořáková and Horsák, 2012;Labaune and Magnin, 2001). ...
... Soil electrical conductivity is a reliable proxy measure of soil mineral richness (Horsák, 2006). Elevation was used as a surrogate for climate (Horáčková et al., 2014). The Ellenberg indicator values (Ellenberg et al., 1992) obtained from vegetation samples were used as a proxy for the soil moisture (Cejka et al., 2007;Čejka & Hamerlík, 2009), and also for the light, soil moisture, soil reaction, and content of soil nutrients (Horáčková et al., 2014). ...
... Elevation was used as a surrogate for climate (Horáčková et al., 2014). The Ellenberg indicator values (Ellenberg et al., 1992) obtained from vegetation samples were used as a proxy for the soil moisture (Cejka et al., 2007;Čejka & Hamerlík, 2009), and also for the light, soil moisture, soil reaction, and content of soil nutrients (Horáčková et al., 2014). Eutrophication was assessed using ecological indicator values of vascular plants (Zarzycki et al., 2002) for assessment of the microspatial distribution of molluscs (Książkiewicz-Parulska & Ablett, 2017). ...
The paper assesses the effect of transformation of soil physical properties on the abundance of micromolluscs in the conditions of an urban park. The studies were carried out in Novooleksandrivskiy Park (Melitopol, Ukraine). An experimental polygon was represented by 7 transects with 18 sampling points in each. The interval between the points in the transect, as well as the interval between transects, was 3 meters. The total area of the polygon was 1,134 m 2. The tree species growing within the polygon were Quercus robur, Sophora japonica, and Acer campestre. Shrubs were represented by Ulmus laevis, Tilia cordata, Celtis occidentalis, and Morus nigra. The locations of the trees and shrubs were mapped. The crowns of tree and shrub plants formed a dense canopy and a shady light regime. The grass cover was practically absent. The soil mechanical resistance, soil aggregate-size distribution, electrical conductivity of soil, soil moisture and bulk density were measured. We recorded 618 individuals of Vallonia pulchella, 120 individuals of Cochlicopa lubrica, and 58 individuals of Acanthinu-la aculeata within the surveyed polygon. We extracted three principal components, which could explain 60.9% of the variation in the feature space of the soil properties. The principal component 1 explained 42.0% of the variation of the feature space and depended on the soil penetration resistance throughout the whole profile, aggregate composition, density, electric conductivity and moisture content of soil. This component reflected a tendency for soil penetration resistance and soil density to increase near recreational trails. The principal component 1 was used to indicate the gradient of recreational transformation of the soil. The principal component 2 was able to explain 10.6% of the variation in the feature space. It negatively correlated with the distance from the recreational trail, soil penetration resistance at the depth of 35 cm or more, soil electrical conductivity, and the proportion of aggregates greater than 3 mm in size. This component positively correlated with soil penetration resistance at 0-5 cm depth and the proportion of aggregates less than 0.5 mm in size. This component can be interpreted as a "halo" from the recreational trail, or a gradient of indirect soil transformations adjacent to the zone of intense recreational load. The principal component 3 was able to explain 8.3% of the variation in the feature space. It positively correlated with soil penetration resistance at the depth of 20-40 cm, the proportion of 0.5-7.0 mm aggregates, and soil moisture. It negatively correlated with the proportion of aggregates larger than 7 mm and smaller than 0.25 mm. This component indicated a variation in soil properties that was induced by causes independent of recreational exposure. The extracted gradients of soil properties significantly influenced the abundance of micromollusc populations. The abundance of all species decreased after increase in recreational load. Micromollusc species responded to direct recreational exposure as plateau (C. lubrica) and asymmetric unimodal responses (V. pulchella and A. aculeata).
... The studies on terrestrial gastropod fauna in poplar woodlands are usually part of ecological and faunistic surveys of floodplain zones near rivers (Bába 1998, Horáčková et al. 2014, Barbato et al. 2020. During a field trip for malacological research of poplar woodlands in the valley of the Bregalnitsa River, a new member of genus Vitrea Fitzinger, 1833 was discovered. ...
... Wet conditions along the valley of the Bregalnitsa River support the presence of third group of species, the hydrophilic and hydro-mesophilic species (N=3): an unidentified taxon of the family Succineidae, Val-lonia enniensis (Gredler, 1856) and Zonitoides nitidus (Müller, 1774). The low number of species of the third group can be explained by the frequent floods in the floodplain zone of poplar forests, when the hydrophilic species preferably occur (Horáčková et al. 2014) and over-domination of few gastropod species in such extreme zones (Bába 1998). ...
A list of 24 terrestrial gastropod taxa from riparian poplar woodlands in the valley of the Bregalnitsa River, Republic of North Macedonia, is presented. A new species of the genus Vitrea is described. Vitrea melovskii sp. n. is the second endemic species of this genus found in the Republic of North Macedonia. It is characterised by the largest umbilicus among the species of Vitrea from North Macedonia.
... The richest species inventories were found for the floodplains of Austria (Reischütz 2014), Germany (Obrdlík et al. 1996), the Slovak part of the Danube (this survey) and the alluvial plain of the Elbe River (Horáčková et al. 2014). From Reischütz's list, we excluded species that were washed into the Danube Plain from the Alps (e.g. ...
Regular diversity surveys are important for monitoring changes in the molluscan fauna's species richness and composition in time, especially in areas of large river floodplains, which are biodiversity hotspots characterised by rapid and dynamic habitat changes. This work brings an annotated list of the terrestrial molluscan fauna from the Slovak part of the Danube Plain and contains several original findings based on field observations. Snails and slugs were collected using visual searches, snails were also sampled using leaf litter collections. A total of 81 terrestrial gastropod species (45% of the total number of land gastropods in Slovakia) from 27 families were found in the 45 sites in the whole surveyed territory. The highest number of species (max. 25 species, median = 18) was recorded in flooded forest habitats, followed by non-flooded forest habitats (max. 20 species, median = 15), the least species occurring in open habitats sensu lato (max. 14, median = 9). The ordination (MDS) showed that open wet communities/sites formed an isolated, relatively compact cluster, flooded and non-flooded gastropod communities form more similar, albeit relatively clearly separated clusters. Communities in open dry sites are the most species-specific and heterogeneous.
... These subsamples were amalgamated, air-dried and all shells were sorted out using sieves of different mesh size. All empty shells, including their fragments, were excluded from analyses in order to reduce potential bias caused by (1) including species that were not living in the locality but that had their shells redeposited by floods, (2) not including species living in the locality whose accumulated empty shells were removed by accidental flooding [74], and (3) a different length of shell degradation time in various floodplain forest types, which depends mainly on humidity [70,75] and topsoil calcium content [76]. For these reasons in our analyses we only used the total numbers of living land snail species (further referred to as ''total species'') and the total number of individuals per species. ...
Studies of plant invasions rarely address impacts on molluscs. By comparing pairs of invaded and corresponding uninvaded plots in 96 sites in floodplain forests, we examined effects of four invasive alien plants (Impatiens glandulifera, Fallopia japonica, F. sachalinensis, and F.×bohemica) in the Czech Republic on communities of land snails. The richness and abundance of living land snail species were recorded separately for all species, rare species listed on the national Red List, and small species with shell size below 5 mm. The significant impacts ranged from 16-48% reduction in snail species numbers, and 29-90% reduction in abundance. Small species were especially prone to reduction in species richness by all four invasive plant taxa. Rare snails were also negatively impacted by all plant invaders, both in terms of species richness or abundance. Overall, the impacts on snails were invader-specific, differing among plant taxa. The strong effect of I. glandulifera could be related to the post-invasion decrease in abundance of tall nitrophilous native plant species that are a nutrient-rich food source for snails in riparian habitats. Fallopia sachalinensis had the strongest negative impact of the three knotweeds, which reflects differences in their canopy structure, microhabitat humidity and litter decomposition. The ranking of Fallopia taxa according to the strength of impacts on snail communities differs from ranking by their invasiveness, known from previous studies. This indicates that invasiveness does not simply translate to impacts of invasion and needs to be borne in mind by conservation and management authorities.
Urbanisation is widely considered as having a large impact on most native species. However, the species response to urbanisation varies among taxonomic groups, and its generalisation might lead to contradictory or incorrect management decisions in urban planning. Land snails, as an understudied group in this sense, are good subjects to study the impact of urbanisation due to their low dispersal capabilities and mobility. The study aimed to determine how land snail diversity patterns and community structure are influenced by urbanisation through an urban-to-rural gradient. A total of 59 terrestrial gastropod species and more than 4600 individuals were recorded at 24 alluvial sites distributed along an urban-to-rural gradient in three Slovak cities (Bratislava, Zvolen and Prešov). Most species belonged to euryecious, hygrophilous and forest specialist ecological groups; seven species were non-native to Slovakia. The results clearly highlight the negative effect of densely built areas on land snail community structure, since the proportion of indigenous and specialist species decreased progressively towards urban sites. The highest mean number of species was found in suburban zones and the lowest in urban zones, suggesting that most species favour intermediate levels of urbanisation. Some species (e.g. Arion vulgaris) were evenly distributed along the urbanisation gradient, supporting the importance of river floodplains as bio-corridors for the dispersal of gastropods.
The diversity of land snails in Leyte Island has not been examined over the past few years. To address this, a survey of macro land snails (> 5 mm in shell height and diameter) in selected forest fragments of Leyte was conducted. A total of 120 quadrats (10 x 10 m) were set in three sampling sites (Inopacan, Baybay, and Maasin) that varies in area size – with Baybay being the largest fragment, followed by Inopacan and Maasin. From a total of 592 individuals, 22 macro land snail species and five families were identified. The macro land snail assemblage was dominated by endemic eupulmonates (Order Stylommatophora) and caenogastropods (Order Architaenioglossa). Among eupulmonates, Family Camaenidae had the most species (10), followed by Trochomorphidae and Achatinidae (two each), and Helicarionidae (one). For caenogastropods, all seven species were under Family Cyclophoridae. Cyclophorus appenidiculatus was the most abundant, representing 16.65% of the total number of individuals. Lissachatina fulica, an invasive land snail, was also documented in all sites. A β-dominated community assemblage was revealed by species accumulation curves with sampling efficiency using a completeness ratio of 1, which indicates a highly efficient sampling method. Detrended correspondence analysis indicated high similarity in species composition among study sites, with two unique species (Subulona cylindracea and Hypselostyla boholensis) recorded in Maasin and two incidental records (Obba bigonia and Helicobulinus sarcinosa). This study yielded 15 new records of macro land snail species during the sampling. There were five species (Hemiglypta semiglobosa, Amphidromus maculiferus, Leptopoma perlucidum, Chloritis leytensis, and Obba bigonia) that were documented on earlier records on the island, but 33 of the previously recorded macro land snail species were not encountered in the study. The community ecology patterns were also documented in the fragmented forests of Leyte, which is very important in local malacofaunal conservation and management.
Floodplain forests are considered as key forest ecosystems in lowland regions of the European temperate zone. Ecosystem services of floodplain forests are essential for maintaining and sustainable management of water resources. The ecological role of floodplain forest ecosystems in the landscape is emphasized in the context of global change because of flood risk management in landscapes along lowland European river. This chapter deals with these important functions of floodplain forests. Authors of the chapter contribute a large amount of their own professional experience and also utilize a large amount from published literature in the field of monitoring, research and management practice of the water regime and its consequences for floodplain forests from an European perspective. The aim of the case study from the Czech Republic is to fill the knowledge gaps related to the monetary evaluation of floodplain forest habitats endangered by the international water management project Danube–Oder–Elbe channel. The case study is based on published and unpublished research material both from the Czech Republic and also from sources of other European countries. The presented conclusions from this chapter can be of interest for the better understanding of the floodplain forests functions and sustainable management of floodplain forests and their protection in an European perspective.
This paper presents a research of mollusc assemblages in the Milešovský Potok floodplain (Northwest Bohemia, Czech Republic). Altogether, 72 mollusc species (70 species of Gastropoda, 2 species of Bivalvia) have been recorded at the selected sites during previous and recent researches in 1947–2010 representing 29% of the total
Czech malacofauna. Widespread forest species dominate there (40% of all recorded species) with some less common woodland species such as Platyla polita, Oxychilus glaber, Macrogastra ventricosa, Sphyradium doliolum, and Perforatella bidentata. The rest of malacocoenoses is formed by mesophile species (22%), hydrophilous species (6%), species of wetlands (8%), freshwater habitats (8%) and species of open habitats (10%). Vertigo angustior, a rare wetland species protected by the NATURA system, and Helicella itala, endangered species of open habitats, were also found. The malacofauna of the Milešovský Potok stream can be used as a model of mollusc assemblages of natural floodplain environment in warm areas of Central Europe.
The recent molluscan assemblages of all floodplain forests on the 256 km long Ohře River were studied (West and Northwest Bohemia, Czech Republic). Altogether, 75 species of terrestrial Gastropoda representing 30% of the total Czech malacofauna, were recorded at sites selected during previous and recent research from 1950−2010. The Ohře malacofauna is impoverished of many forest and floodplain species in comparison to molluscan assemblages of smaller Bohemian rivers to the west and northwest. The richest molluscan assemblages occur on the upper part of the river, while the middle and lower parts are very poor. Low alpha-diversity of these parts of the Ohře River can be explained by (1) intensive agriculture in floodplain areas of the middle part of the river, (2)
the migration barrier of the Nechranice Dam between the upper and middle river parts, and (3) long-term human influence on the lower part of the Ohře River during the Holocene.
Altogether, 78 terrestrial mollusc species were recorded on 31 plots in a stretch of the Tichá Orlice River valley between the cities Choceň and Letohrad (East Bohemia, Czech Republic) in 2007 and 2009. This region harbours 46% of the total terrestrial mollusc fauna of the Czech Republic. The fairly high species richness corresponds to a high habitat diversity and species pool of the region that includes Alpine and Carpathian elements. Of prime conservation importance is a high share of rare and endangered species (EN-2, VU-9, NT-14 species) and species mostly having an isolated population there from the main distribution range. This region is a real hotspot of forest gastropods in Transalpine Europe.
The robustness of quantitative measures of compositional dissimilarity between sites was evaluated using extensive computer simulations of species’ abundance patterns over one and two dimensional configurations of sample sites in ecological space. Robustness was equated with the strength, over a range of models, of the linear and monotonic (rank-order) relationship between the compositional dissimilarities and the corresponding Euclidean distances between sites measured in the ecological space. The range of models reflected different assumptions about species’ response curve shape, sampling pattern of sites, noise level of the data, species’ interactions, trends in total site abundance, and beta diversity of gradients.
The Kulczynski, Bray-Curtis and Relativized Manhattan measures were found to have not only a robust monotonic relationship with ecological distance, but also a robust linear (proportional) relationship until ecological distances became large. Less robust measures included Chord distance, Kendall’s coefficient, Chisquared distance, Manhattan distance, and Euclidean distance.
A new ordination method, hybrid multidimensional scaling (HMDS), is introduced that combines metric and nonmetric criteria, and so takes advantage of the particular properties of robust dissimilarity measures such as the Kulczynski measure.
The paper deals with historical development of floodplain forests in the area of Vrapač National Nature Reserve in the floodplain of the Morava River (Protected Landscape Area Litovelské Pomoraví, Czech Republic). The aim of this paper is to contribute to a better understanding of the anthropogenic influences that have over centuries led to the present state of floodplain forests in the study area. Thus, it will be possible to define more efficiently the management plan of this floodplain forest ecosystem.
The malacofauna of 37 topogenous, soligenous and mixed fens in Dovrefjell consists of 18 snail species and three slugs, with 1-10 species per locality and 5-358 individuals per 10 l litter; at most localities single species dominate strongly. Number of species and individuals and the dominance structure of the malacocenoses depend on fen type, litter pH and Ca content, and altitude. Two of the four records of Vertigo parcedentata are new. -Author
It is difficult to define precisely determinant environmental factors that explain land snail distribution and abundance, and most variables are often interrelated. In addition, studies have generally examined only a limited number of environmental variables, yielding a partial and local habitat description. Recognised determinant factors are: Climate, vegetation and soil, Competitive interactions, historical factors and spatial structure are rarely included, although they could generate biogeographic patterns on a local or regional scale. The goal of the present work is to evaluate land snail habitat complexity by examining a wide range of environmental variables. Land snails from open environments were studied in a Provence range, the Grand Luberon, characterised by low variations in pH and calcium content. Grasslands on the ridges are maintained by sheep grazing. A stratified sampling was chosen according to altitude and vegetation structure. Sites were sampled throughout the range. Different vegetation structure types were analysed, from low grasslands to shrublands. Thirty-eight environmental variables were noted for each site. They described: (1) topography and climate, (2) habitat structure, (3) flora, and (4) spatial structure of snail communities. The main analytical method used was the partial Canonical Correspondence Analysis which yielded a partition of species variation into several independent components. The four environmental variable groups were used separately. We obtained a partition of ecological variation which emphasised the predominance of habitat structure over floristic composition and the important role played by environmentally independent spatial variables. Nevertheless, it remains difficult to discriminate between the influence of climatic factors s.s., historic events and/or biotic factors within the altitudinal gradient.
This paper considers the numbers of species and individuals of terrestrial snails in small plots (quadrats) of different sizes (0.0625 m², 0.25 m², 0.56 m²) in three types of treeless fen sites differing in calcium content. It compares the results of considering only live individuals or of combining these with empty shells. In two of the three sizes of plots and all fen (mineral level) types there was a clear increase of species when empty shells were included. In very calcium rich sites, empty shells contribute significantly to a summary of the fauna in the plot over several years, and can improve the inventory efficiency of sampling. However, when comparisons are made among sites with different soil chemistry, estimates of densities and relative abundances will be distorted, because shells decay at different rates among them. Hence, in any studies concerned with densities or spatial heterogeneity within sites it is necessary to distinguish between live individuals and empty shells.
Ellenberg indicator values for moisture, nitrogen and soil reaction were correlated with measured soil and vegetation parameters. Relationships were studied through between‐species and between‐site comparisons, using data from 74 roadside plots in 14 different plant communities in The Netherlands forming a wide range.
Ellenberg moisture values correlated best with the average lowest moisture contents in summer. Correlations with the annual average groundwater level and the average spring level were also good. Ellenberg N‐values appeared to be only weakly correlated with soil parameters, including N‐mineralization and available mineral N. Instead, there was a strong relation with biomass production. We therefore endorse Hill & Carey's (1997) suggestion that the term N‐values be replaced by ‘productivity values'. For soil reaction, many species values appeared to need regional adjustment. The relationship with soil pH was unsatisfactory; mean indicator values were similar for all sites at pH > 4.75 because of wide species tolerances for intermediate pH levels. Site mean reaction values correlated best ( r up to 0.92) with the total amount of calcium (exchangeable Ca ²⁺ plus Ca from carbonates). It is therefore suggested that reaction values are better referred to as ‘calcium values'.
Using abundance values as weights when calculating mean indicator values generally improved the results, but, over the wide range of conditions studied, differences were small. Indicator values for bryophytes appeared well in line with those for vascular plants. It was noted that the frequency distributions of indicator values are quite uneven. This creates a tendency for site mean values to converge to the value most common in the regional species pool. Although the effect on overall correlations is small, relationships tended to be less linear. Uneven distributions also cause the site mean indicator values at which species have their optimum to deviate from the actual Ellenberg values of these species. Suggestions for improvements are made.
It is concluded that the Ellenberg indicator system provides a very valuable tool for habitat calibration, provided the appropriate parameters are considered.
Inventories of land molluscs based on samples are liable to biased sampling error, because species that are present may be missed. Such errors may give a false impression of the degree of difference between faunas from similar sites, and they are confounded with genuine heterogeneity, which has considerable ecological and conservation significance. The statistical properties of such errors are examined briefly in the context of sample size and the frequency distribution of species. The effectiveness of different sampling strategies is assessed, taking account of the different life cycles and behaviour of various mollusc species. Taking random quadrats alone is not an efficient method for inventory; a combination of visual search and extraction from litter and soil is required. A set of practical guidelines is given, and the importance of good inventories, especially in oligotrophic habitats, is underlined.
There is an ongoing debate on the causes of the latitudinal diversity gradient, but diversity decline towards high latitudes is poorly documented for many invertebrate taxa. Therefore, we sampled land snail assemblages at 79 sites and in various habitat types in central Yakutia, a region with extremely continental, cool and dry climate. We tested whether habitats lacking suitable shelters for winter survival harbour less species than those with vegetation cover that softens climatic extremes. Both local species diversity and regional species diversity were extremely low: 13 species were recorded in total with an average of 1.4 species per site. While the majority of grassland sites were without snails (26 of 34 sites), forest sites supported at least one snail species in most cases (38 of 45 sites). Within grasslands, snail occurrences were associated with a higher herb-layer biomass. Numbers of snail species correlated with the amount of available calcium only in forests, in which species accumulation towards more favourable habitats was possible due to softening of climate harshness. As minute snails are known to be effective passive dispersers and the study area was not glaciated during the last glacial stage, there was certainly enough time for colonization of all favourable habitats. Our results suggest climatically driven limitations of both local and regional land snail diversity in central Yakutia. We conclude that the hypothesis of climate harshness remains the most probable explanation of a sharp drop in land snail diversity in high-latitude areas with cold climate.
A malacological study at 41 forest sites in the Southern Urals (Bashkortostan, Russia) conducted in 2007 gave the first quantitative data about land snail assemblages from this region. These data were used to identify the main patterns and predictors of snail species richness and composition, to assess the relations of snail assemblages to vegetation using detrended correspondence analysis (DCA) and to explore the hypothesis that forests of this area are modern analogues of the Early Holocene forests of Central Europe. In total, we recorded 29 snail species. Species richness per site was very low (0-14 species) although environmental conditions at many sites were generally favourable for snails (high calcium supply, abundant moisture and undisturbed character). Variation in species richness and composition was almost exclusively governed by local environment factors, rather than differences in location. The main gradient of vegetation composition (expressed as site scores on the first DCA axis), calcium and nitrogen content in herb biomass, and altitude were identified as the best correlates of species richness and compositional variation in snail assemblages. Snail species significantly accumulated towards more fertile, calcium-rich and lowland sites; the richest faunas were in alluvial alder forests and mesic lime-maple-elm forests. Several features such as low snail species richness, predominance of generalist species with wide distributions, and broader realized niches of particular species in the Southern Ural forests relative to their niches elsewhere, corresponded to those of fossil assemblages from the Early Holocene deposits of Central Europe. This supports the hypothesis that the Southern Urals snail faunas provide good analogues for those of Early Holocene assemblages of Central Europe. Our data also suggest that the very limited species pool, mostly of widely distributed species with good dispersal abilities, results in species-poor assemblages that are structured mainly by environmental filtering.
One of the problems with biodiversity for palynologists is that their samples come from an unbounded area and source area varies with both pollen/spore type and vegetation type. There have been two broad approaches to the problem of inferring diversity from pollen/spore samples; firstly the use of pollen type richness as a proxy for species richness, and secondly the ‘identification’ of past vegetation communities aided by ecological inference and historical or modern data concerning species affinities and typical diversity. The estimation of biodiversity from pollen analysis depends upon the pollen count, taxonomic precision, source strength for individual types and dispersal/transport of pollen from source areas to the site. A transect of surface pollen samples is used here to test the effect of a vegetation boundary on pollen/spore diversity and compare the pollen/spore diversity with the species richness of the woodland. Palynological richness (at a constant count sum) does, to some extent, reflect changing local vegetation along the transect. Type count curves also reflect the changes in vegetation type along the transect due to the partial influence of species richness on pollen/spore richness. This study suggests that depending upon the woodland composition, the woodland may not entirely drown-out the pollen signal of the surrounding vegetation, and that a small woodland may be more representative (as a sampling site) of the valley floor diversity than a raised mire. The surface transect is also used in the interpretation of Medieval pollen levels from The Gearagh.
Zusammenfassung: Wirth, V. 2010. Ökologische Zeigerwerte von Flechten – erweiterte und aktualisierte Fassung. – Herzogia 23: 229 –248. Eine neue Ausgabe der Liste der ökologischen Zeigerwerte von Flechten wird vorgelegt. Die Werte der bislang berücksichtigten Arten wurden überprüft und gegebenenfalls korrigiert. 58 weitere Arten wurden aufgenommen. Somit liegen für insgesamt 516 Arten Indikatorwerte für wichtige klimatische Faktoren (Licht = L, Temperatur = T, Kontinentalität = K, Feuchte = F) und Substrateigenschaften (pH = R, Eutrophierung = N) vor. Außerdem wird ein Verfahren zur Abschätzung der klimaökologischen Ozeanität (KO) anhand der Zeigerwerte vorgelegt. Da die klima-ökologische Ozeanität eine thermische und eine hygrische Komponente hat, lässt sich der entsprechende Zeigerwert aus den Zeigerwerten für Kontinentalität und Feuchte nach der Formel KO = (10 – K + F) : 2 errechnen. Abstract: Wirth, V. 2010. Ecological indicator values of lichens – enlarged and updated species list. – Herzogia 23: 229 –248. A new edition of the species list of ecological indicator values of lichens is presented. Values of the hitherto considered species have been checked and corrected where appropriate. Fifty-eight additional species have been included. Overall, indicator values for important climatic factors (light = L, temperature = T, continentality = K, moisture = F) and substrate properties (pH = R, eutrophication = N) are now available for 516 species. A procedure to assess the eco-climatic oceanity (KO) with the help of the indicator values is presented. Since the eco-climatic oceanity has a temperature and a moisture component, the indicator value of eco-climatic oceanity can be calculated with the formula KO = (10 – K+F) : 2.
In three areas of the English Midlands, composition and diversity of hedgerow snail faunas are influenced both by historical and environmental differences between hedges. Soil aciditv and climate are the most important environmental factors. Hedges originating in or near woodland have richer faunas than those planted in open fields, and some snail species are indicators of woodland origin. Snail diversity also increases with the age of the hedge, but this effect is slight in hedges over 100 years old. It is suggested that these differences are primarily due to the poor dispersal of snails rather than to existing environmental differences between hedges of differing age and origins, and the results are compared with the very similar ones obtained for plants. Historical influences on the distribution ol slow-dispersing organisms may be of very general importance, even in comparisons of adjacent habitats with considerable temporal stability.
This paper presents geomorphic, soils and palaeoecological data from a small sub-catchment in the English Midlands in an attempt to provide an integrated picture of Holocene landscape change. The area used has also been the focus of a multi-disciplinary and long-term archaeological survey (Raunds Area Project) and so has a wealth of archaeological and historical data which can be related to the environmental record. The paper combines these data, much of which are only published in the archaeological literature with new interpretations based upon unpublished data and new data particularly from the hillslopes and new radiocarbon dating from the valley floor. It is inferred that despite a long history of pastoral and arable agriculture (since the Neolithic/Bronze Age), colluviation on lower slopes, significant soil redistribution and overbank alluviation only began to a measurable extent in the Late Saxon–Medieval period (9th Century AD onwards). It is suggested that this is due to a combination of land-use factors, principally the laying out of an intensive open field system and the establishment of villages combined with a period of extremes in climate well known throughout Europe. Indeed the critical element appears to have been the social changes in this period that created this regionally distinctive landscape which happened to have a high spatial connectivity and facilitated intensive arable production with high tillage rates. Intense rainfall events during this period could therefore detach and mobilize high volumes of soil and the open field system facilitated transport to slope bases and valley floors. The need for detailed and spatially precise land-use data in order to interpret accelerated landscape change is stressed.
Summary. Recent work by Reiss and Ogden provides a theoretical basis for sometimes preferring restricted maximum likelihood (REML) to generalized cross-validation (GCV) for smoothing parameter selection in semiparametric regression. However, existing REML or marginal likelihood (ML) based methods for semiparametric generalized linear models (GLMs) use iterative REML or ML estimation of the smoothing parameters of working linear approximations to the GLM. Such indirect schemes need not converge and fail to do so in a non-negligible proportion of practical analyses. By contrast, very reliable prediction error criteria smoothing parameter selection methods are available, based on direct optimization of GCV, or related criteria, for the GLM itself. Since such methods directly optimize properly defined functions of the smoothing parameters, they have much more reliable convergence properties. The paper develops the first such method for REML or ML estimation of smoothing parameters. A Laplace approximation is used to obtain an approximate REML or ML for any GLM, which is suitable for efficient direct optimization. This REML or ML criterion requires that Newton–Raphson iteration, rather than Fisher scoring, be used for GLM fitting, and a computationally stable approach to this is proposed. The REML or ML criterion itself is optimized by a Newton method, with the derivatives required obtained by a mixture of implicit differentiation and direct methods. The method will cope with numerical rank deficiency in the fitted model and in fact provides a slight improvement in numerical robustness on the earlier method of Wood for prediction error criteria based smoothness selection. Simulation results suggest that the new REML and ML methods offer some improvement in mean-square error performance relative to GCV or Akaike's information criterion in most cases, without the small number of severe undersmoothing failures to which Akaike's information criterion and GCV are prone. This is achieved at the same computational cost as GCV or Akaike's information criterion. The new approach also eliminates the convergence failures of previous REML- or ML-based approaches for penalized GLMs and usually has lower computational cost than these alternatives. Example applications are presented in adaptive smoothing, scalar on function regression and generalized additive model selection.
Devensian and Flandrian deposits at and below the level of the floodplain of the River Nene (central England) are described. At Little Houghton fossiliferous deposits of Middle Devensian age underlay fluvial gravels. Fossiliferous silts or muds within fluvial gravel sequences at Titchmarsh and Orton Longueville are shown to be of Late Devensian age. River channel infills overlying the gravels at Titchmarsh and Orton Longueville are of late-Flandrian (approximately Iron Age) age. Fossil plants (pollen and macrofossils), molluscs and mammals are described from most of these deposits. A limb bone of the giant deer Megaceros giganteus was found in the Late Devensian deposits at Orton Longueville. This species apparently became extinct in the Late Devensian and there are only two other records from England in this substage.-from Authors
A coppice woodland in Sussex has been surveyed for molluscs (quantitatively for snails and qualitatively for slugs) and measurements taken of pH, free chalk, litter and vegetation, with the aim of determining whether coppicing has an effect on snails. The fauna and population structure are described. No direct correlations have been found between age of coppice compartment and either diversity or abundance of snails, although significant relationships were obtained between age and litter depth and between age and percentage vegetation cover. However, two species of snail were found mainly in the earlier or later stages (Vitrina pellucida, Oxychilus alliarius). A negative relationship exists between snail diversity and abundance, and may reflect, in this particular woodland, the increased dominance of Carychium tridentatum. However, comparison with other studies indicates that a positive relationship between diversity and abundance is also possible. The pH has a significant, positive relationship with snail species richness and abundance in the community as a whole. A number of individual species (Carychium tridentatum, Discus rotundatus, Aegopinella pura, Vitrea contracta, Pomatias elegans and Vitrina pellucida) show strong positive relationships with pH, and others (Nesovitrea hammonis and Punctum pygmaeum) show pronounced negative relationships. Litter depth and litter percentage cover appear to play an important role, with several species achieving peak numbers at 2 cm depth of litter. Soil particle size may also be a factor affecting richness and abundance. It is suggested that the main effects of coppicing on snails could be caused by the associated initial reduction in litter. This would affect litter dwelling species most. The arboreal and dead-wood favouring species are likely to be at a relatively low level of abundance because of the removal of dead wood associated with coppicing.
The species composition and abundance of land gastropods were investigated at 24 sites in the area of the Danubian floodplain and the adjacent part of the Zitny ostrov region during 1990-1997. 50 species of 21 families were recorded in the area. The most abundant were (in decreasing relative abundance): Aegopiaella nitens, Monachoides incarnatus, Petasina unidentata, Arianta arbustorum, Vitrea crystallina, Zonitoides nitidus, Carychium minimum, CochJcopa lubrica, Urticicola umbrosus, Trichia striolata, Cochlodina laminata, Vallonia costata, Fruticicola fruticum, Semilimax semilimax, Alinda biplicata, Pseudotrichia rubiginosa, Cepaea hortensia, Punctum pygmaeum and Succinea putris. Of the total number of 50 species, 11 (22.0%) were euryecious, 8 (16.0%) were tolerant forest species, 6 (12.0%) were strongly hygrophilous, 4 (8.0%) belonged to the ecological group of forest, steppe and open-country species, 3 (6.0%) were hygrophilous and forest hygrophilous species and two (4.0%) were bush, forest-steppe and xericolous species. The results are discussed in relation to previous studies from the territory of the Danubian floodplain which originate from the period before the construction of the GabCikovo power project.
We studied snail assemblages at 39 plots in hay meadows of the White Carpathians, Czech Republic. We recorded snails quantitatively in 1 m² quadrats, along with vegetation and several measured variables in the same plots in order to investigate the influence of selected environmental factors on meadow snail species composition and richness. The study aimed to determine the extent to which it is possible to use vegetation as a predictor of land snail composition by comparing the predictive power of three groups of variables: (i) measured variables and climatic factors, (ii) vegetation, and (iii) Ellenberg indicator values for plants estimated from plant composition. Detrended correspondence analysis revealed that both snail and plant assemblages were strongly affected by the main environmental gradient running from calcium-poor, wet and cool upland sites to calcium-rich, dry and warm lowland sites. The main changes of vegetation and snail species composition were highly correlated (rs = 0.77, p < 0.001). Soil calcium content and moisture were the most important factors, which explained most of the variation both in the snail and plant assemblages. The interaction of these two factors was even stronger but it was not possible to separate the influence of particular variables on snail species composition and to determine which of these variables made the greatest contribution to the observed pattern. Using the variance partitioning approach, we found that most variation in snail species data was jointly explained by all three groups of variables (i.e., measured variables and climatic factors, vegetation, and Ellenberg indicator values for plants). Even so, the net effects of both vegetation and measured variables were significant. This indicates that vegetation could describe important environmental controls of land snail distribution, even those that are difficult or even impossible to measure directly. We conclude that vegetation composition can be very useful predictor in snail community ecology studies.
We studied changes of terrestrial snail assemblages over a gradient of soil moisture using 60 sampling plots in the White Carpathian Mountains of the south-eastern Czech Republic. We used within-site design to control for confounding effects of site characteristics other than humidity, and we directly measured soil moisture along nine transects at distinct locations. Each transect had from 4 to 16 plots, and it was laid down from wet calcium-rich spring fen habitats to semi-dry meadows in the fen surroundings. We observed a sharp moisture gradient along each transect, with the measured soil moisture varying from 97% in fen plots to 19% in semi-dry grassland plots. Altogether 29 land snail species and 4,213 live individuals were collected. Species richness of land snails varied from 2 to 11 species per plot. However, we did not observe any significant linear or unimodal response of species richness or total abundances to measured soil moisture. In contrast, sharp compositional changes along studied transects were found, suggesting differences in species preference to soil moisture conditions at fine, within-site scale. Among 21 species with the frequency higher than five, 10 (after a Bonferroni correction) showed a significant response to soil moisture. Three species expressed significant affinity to drier plots, five species were more abundant in moister plots and only two species preferred middle values. In several previous studies, both linear and hump-shaped relation between soil moisture and number of land snail species were documented. This raised questions about general response of land snails to soil moisture and the importance of possible bias caused either by using only estimated values of site moisture or sampling in distinct sites differing also in other environmental factors that might potentially overtopped importance of soil moisture for land snail distribution.
The influence of environmental factors on the distribution of land molluscs in woodland habitats is discussed on a basis of a field study, preference tests, and breeding experiments. Effects of the calcium content and of the pH value of the foerna upon species number and abundance are demonstrated. It is known that in the leaves of some tree species, Ca citrate and other relatively soluble Ca salts dominate, while others are rich in Ca oxalate. In the breeding experiments, Ca citrate had a considerable, and Ca oxalate a moderate positive effect upon the reproduction of Discus rotundatus (Müll.) and Cochlicopa lubrica (Müll.). /// На основе полевых исследований обсуждаются влияние внешних факторов на распределение наземных моллюсков в лесных местообитаниях, а также результаты опытов по изучению преферендума и скрещиванию. Уста-новлено влияние содержания Са и значения рН подстилки на кодичество видов и численность животных. Известно, что в листве некоторых пород деревьев преобладает цитрат Са и другие, относительно хорошо раство-римые соли Са, в то время, как в других породах доминирует оксалат Са. В опытах по скрещиванию зарегистрировано значительное положи-тельное влияине цитрата Са и менее существенное влияние оксалата Са наразмножение Discus rotundatus (Müll.) и Cochlicopa lubrica (Müll.).
Alluvial hardwood forests (Querco-Ulmetum) are found on flooded but well-drained and fertile soils of big European floodplains. High disturbance regime of the river combined with a relatively warm and moist local climate of the floodplain valley are the main factors responsible for the original features of this community (dendrofloras richness, structural and successional complexity, high productivity). This paper summarizes available information from this forest community in Europe with emphasis with the Querco-Ulmetum of the Rhine valley (Alsace, France). The results obtained in this study area from twenty years of team work demonstrate that the floristic composition varies within sectors of a single stream with changes in channel slope. Floristic and structural features of hardwoods change too in the different parts of the upper Rhine according to a flood-risk gradient.
Environmental factors influencing the occurrence of land molluscs (calcium, pH, moisture, vegetation) were studied in five types of woodland habitat, chosen in a CaCo3-free area. The necessary supply of Ca occurs in organic material, mainly in litter and foerna. Correlations between the Ca content in the foerna and abundance of snails were found and also between Ca and number of mollusc species. Different Ca salts dominate in the leaves of different tree species. The relatively high content of Ca oxalate at most oak wood localities has no direct pH increasing effect, while there is a pH increase in the soil surface at localities with ash, lime, maple and elm, probably depending upon the fact that in litter from these trees more soluble and therefore more alkaline Ca salts, e.g. Ca citrate, dominate. Forests containing the latter tree species often have rich mollusc faunas. Correlations between soil moisture and abundance of snails were also found. /// Были исследованы факторы окружающей среды (наличие кальция, pH, растительности, степень сырости), ьвліияюще на существование земельных (сухопутных) слизняков. Для исследования были выбраны 5 типов "Woodland Habitat" из окружающей местности без наличия CaCO3. Необходимое снабжение кальцием происходит посредством органических веществ, находящихся, главным образом в помете, гнилой личтве и хвое. Было установлено соотношение между листвой, содержащих кальций, и наличия члиток. Различные соли кальция преобладают в листве разных типов деревьев. Оксалат кальция, а также и легко разводимые соли кальция, напр. щавелевокислый кальций (цитратнокислый кальций), очевидно влияков в многих отношениях. Было также установлено соотношение между степенью сырости земли и наличия члиток.
The Polabi lowland is one of the most important agricultural areas in Central Europe. Since the Neolithic Age, agriculture has prevented full expansion of the mixed deciduous forest. We studied the succession of molluscan assemblages and/or fossil pollen in this area to answer the question as to how long the canopy forest could survive ongoing human impact. Environments suitable for the fossilization of these two fossil types differ, and the joint occurrence of both is rare. However, the 0.75 m deep profile of alluvial loams and clays situated in the irregularly inundated floodplain area of the Dubanka stream yielded material rich in both mollusc shells and pollen. Very rich molluscan assemblages occur only in a 45 cm thick layer, which was dated using the AMS radiocarbon method to the Bronze Age (1796-1258 BC). The molluscan assemblages consist of continuously occurring rare deciduous woodland species (such asDiscus perspectivus, Platyla polita, Cochlodina orthostoma, Ruthenica filograna) and species of relict wetlands (e.g. Perpolita petronella, Vertigo angustior, V. antivertigo, Vallonia enniensis). Pollen analyses also suggest the presence of wetland assemblages, with a huge proportion of alder in the central part of the succession followed by willow. The deciduous forests consist of elm (Ulmus), oak (Quercus), lime tree (Tilia), maple (Acer) and hazel (Corylus). Pollen grains of spruce (Picea), white fir (Abies) and beech (Fagus) confirm the late Holocene age of the profile. These results provide evidence of a woodland and wetland mosaic which still covered this landscape during the Bronze Age, in contrast with the present-day monotonous open lowland.
Within river corridors, the distribution of plant species and communities is heavily influenced by hydrological and geomorphological processes. Furthermore, the vegetation can have a direct influence on the detailed character and rate of hydrogeomorphological processes. This paper reviews such interactions at a variety of spatial scales ranging from vegetation gradients across entire floodplains from hillslope to river channel, to the local influences of bank vegetation and in-channel accumulations of woody debris.
As an introduction to the special issue on European floodplain forests, this paper reviews the fundamental hydrological and geomorphological controls on floodplain biodiversity and river-forest interactions. The role of the energy/slope gradient and channel conditions (including number of channels) can be seen as critical in determining the nature and dynamics of floodplain woodland and biodiversity. These factors also control the processing of materials and nutrients in forested floodplains. The biogeochemistry of floodplain forests is complicated by multi-dimensional interactions between substrate, hydrology and vegetation which include longitudinal interactions (up and downstream), and vertical interactions (e.g. between channels and banks and live and dead-water zones). All of these factors complicate the application of the river continuum concept as do natural variations caused by geomorphological inheritance and multiple channels. The distribution and status of European floodplain woodlands and the history of floodplain forests in the British Isles are briefly outlined. Lastly the paper considers the possibilities for the partial afforestation of some British Floodplains and the potential environmental benefits.
Molluscs, vegetation and water chemistry were investigated at 48 spring fens situated in the borderland between the Czech Republic and Slovakia in 1997-2000. The purpose of this study was to test whether the gradient from mineral-poor to mineral-rich fens is reflected in the composition and species richness of mollusc communities, and to determine the importance of vegetation in predicting the mollusc community composition. A cluster analysis of mollusc communities separated the fens studied into five basic Clusters which accord well with the results of detrended correspondence analysis (DCA). These clusters are arranged along the first DCA axis following the poor-rich trophic gradient. Ca, Mg, Fe, K, pH and conductivity are strongly correlated with the first DCA axis of the mollusc data. Similarly, Ca, Mg, Fe, pH and conductivity explain a substantial part of species-data variation, as verified by separated canonical correspondence analyses (CCAs) with a single variable. When sites with Sphagnum spp. were excluded, no significant correlations with K, pH and conductivity were found, whereas the significance of correlation with Fe increased markedly. Site classifications based on mollusc data are applicable to vegetation data and Nice versa. Vegetation composition is a more important factor for explaining the variation in mollusc species than water chemistry when both are included in two separated CCAs as constraining variables. We found a linear correlation between mollusc species richness and water calcium concentration in the poor fens. In the rich fens, such a correlation was not found, and species richness was dependent on other abiotic and biotic factors, namely the Fe concentration and the water regime.
Quantitative analyses of the snail assemblages of four a priori defined categories of grassland sites, characterized by soil moisture, land use and management, were conducted in SW Germany. Topsoil pH and calcium content were determined for each of 39 sites. The objectives were to study the effects of these habitat characteristics on snail density, species richness and quantitative structure of the land snail assemblages. With one exception, no significant relationships between soil pH (as a proxy for Ca supply) and the total numbers of individuals and species at the four site categories were observed. Snail density and species richness on groundwater soils, represented by rarely mown sedge stands and regularly mown meadows, were clearly higher than on intermediate moisture soils (as defined by the climatic water balance) of regularly mown meadows, indicating that soil moisture was the most important factor accounting for these differences. Furthermore, we observed specific conditions associated with the presence of trees in the category of meadow orchards on intermediate moisture soils. There, numbers of individuals and species were significantly higher than in the meadows on intermediate moisture soils. A posteriori cluster analysis of quantitative similarity of all snail assemblages showed that soil moisture accounts for the major differences between the site categories with respect to snail density, species richness and quantitative composition of the grassland snail assemblages. As these results are in contrast to the findings of many woodland studies, we suggest that the occurrence or abundance of certain species in the site categories are explained by land management, especially by frequent disturbances at the soil surface caused by mowing.
Terrestrial gastropods were collected in central Maine from June to November 1971 to study their distribution, relative abundance, and habitat preferences. Gastropods were widespread, but not abundant. Thirty-five percent of the 1626 gastropods collected were slugs. Thirty-seven snail species, including eight slug species, were found. Discus cronkhitei and Zonitoides arboreus were the most commonly collected gastropods: Deroceras reliculatum and Pallifera dorsalis were the most common slugs. Snails (excluding slugs) were more abundant in the northwestern portion of central Maine, whereas slugs were more abundant in the southeastern portion. Slugs were significantly less abundant in coniferous forests than in deciduous or mixed forests, but snail numbers (excluding slugs) in the three forest types were not significantly different.
The in¯uence of soil exchangeable cations and aluminium content on the distribution of various terrestrial gastropods was investigated. Calcium was the most important factor, though aluminium and magnesium content also had some effect. Potassium and sodium had no signi®cant in¯uence on distribution. The species most sensitive to the factors analysed were Cochlicopa lubrica, Vertigo pygmaea and Carychium tridentatum.
This study investigated the influence of edaphic factors on the distribution of 17 terrestrial gastropod species over a large area of the northwest Iberian Peninsula. A total of 498 gastropod/soil samples were obtained, and a total of 19 edaphic variables determined. The resulting data matrix was analysed by detrended canonical correspondence analysis (DCCA). Our results indicate that the gastropods of the study area can be grouped on two types of criteria: first, chemical criteria (notably pH, cation exchange capacity, and Al content), and secondly physical criteria (notably texture and moisture content). In view of distribution with respect to these factors, two well-defined groups can be identified: one comprising Acanthinula aculeata, Euconulus fulvus, Punctum pygmaeum, Columella aspera and Oxychilus alliarius preferring coarse-textured acid soils, the
other comprising Cochlicopa lubrica, Vertigo pygmaea, Zonitoides excavatus, Carychium tridentatum, Deroceras reticulatum and Deroceras lombricoides preferring wetter, finer-textured, less acid soils. Arion intermedius and Ponentina subvirescens were in general indifferent to the edaphic factors considered.
Geomorphological and palaeoenvironmental research on Holocene sedimentation in the Mue valley provides evidence for fluvial
system changes related to climate and human activities in Normandy, a poorly studied area of the Paris basin. The 24-km long valley
bottom has been investigated through a systematic survey. It shows an original longitudinal sedimentary pattern in relation with valley
morphology and local geological controls. Minerogenic, tufaceous and peaty deposits provide opportunities for multi-proxy analyses
and radiocarbon dating control. Sedimentation began around 9500 14C BP with silt deposition in a meandering system. The Boreal
and the Lower Atlantic periods (8500–6000 14C BP) were mainly characterized by unlithified calcareous tufa. Locally, these deposits
are very thick (7 to 13 m). The tufa formed barrages across the valley bottom, providing an autogenic control on upstream
sedimentation. During the Upper Atlantic period (6000–4700 14C BP), the valley experienced a decrease in calcareous sedimentation
and the development of organic deposits. At the beginning of the Subboreal (4700–3500 14C BP), peat deposits expanded, especially
behind the tufa barrages. The valley bottom was characterized by large marshy areas whereas the regional vegetation was
progressively modified by human activities. At the end of the Subboreal (3300–3000 14C BP) the infilling of the valley by calcareous
silt was caused by an increase of river activity related to climatic and land use changes. From the Iron Age and Gallo-Roman periods
(2800–1700 14C BP), the valley bottom was filled by silty overbank deposits related to an increase of soil erosion. The slopes and
river system were once again coupled and the fluvial system functioned as a continuum from upstream to downstream. The alluvial
record of the Mue valley reflects a broad regional pattern of environmental changes but presents particular features, which highlight
the need of longitudinal studies to take into account spatial and temporal discontinuities of Holocene hydro-sedimentary systems, even
in small order valleys.
The aim of this study was to assess the role of river floodplains as biocorridors for terrestrial snail dispersal. We hypothesised that assemblages in the river alluvium should be more homogeneous in species composition than those in the forest slopes above the river. We also studied the effect of rivers as barriers on the assemblage composition of snail species inhabiting slopes of riverine valleys. The study was conducted on 33 woodland plots arranged in three parallel transects in the Tichá Orlice river valley (E Bohemia, Czech Republic). One transect was in an altered river floodplain and the remaining two on the slopes of the river valley. As expected, the median value of the Jaccard similarity coefficient was highest in the floodplain (50%), although significant difference was obtained in comparison with assemblages of only one slope transect. Further analysis showed that snail assemblages were mostly affected by environmental factors such as humidity and soil calcium content; connectivity played rather minor role.
Patterns of litterfall and decomposition in adjacent floodplain and upland forest communities were investigated at Robert Allerton Park in central Illinois. Floodplain and upland litterfall were similar in terms of dry weight and most nutrients, and were higher than litterfall for other similar forest communities. Leaf litter decomposed rapidly at the floodplain site, and substantial amounts of nutrients were transferred to the mineral soil prior to flooding. This may have been advantageous to individuals of the forest community because the mineral soil nutrient pool was enriched prior to removal of forest floor litter by spring floods. Dry weight loss from leaf litter in the upland forest was much slower than for floodplain litter. Retention of N during leaf litter decomposition was high, indicating a probable demand for this element by heterotrophic decomposer organisms. Assimilation of N from external sources suggests that leaf litter may act as a temporary sink for N. Calcium was moderately retained, P was lost at the same rate as dry weight, and K, Mg, and Na were rapidly leached. This study shows that differences in species characteristics and variability of the physical environment in floodplain and upland forests produce contrasting patterns of nutrient transfer. Forest Sci. 28:667-681.
Aim
The goals of this study were to: (1) compare water conductivity and pH as proxy measures of mineral richness in relation to mollusc assemblages in fens, (2) examine the patterns of mollusc species richness along the gradient of mineral richness based on these factors, (3) model species–response curves and analyse calcicole–calcifuge behaviour of molluscs, and (4) compare the results with those from other studies concerning non-marine mollusc ecology.
Location
Altogether, 135 treeless spring fen sites were sampled within the area of the Western Carpathians (east Czech Republic, north-west Slovakia and south Poland; overall extent of study area was 12,000 km2).
Methods
Mollusc communities were recorded quantitatively from a homogeneous area of 16 m². Water conductivity and pH were measured in the field. The patterns of local species diversity along selected gradients, and species–response curves, were modelled using generalized linear models (GLM) and generalized additive models (GAM), both using the Poisson distribution.
Results
When the most acid sites (practically free of molluscs) were excluded, conductivity expressed the sites’ mineral richness and base saturation within the entire gradient, in contrast to pH. In the base-rich sites, pH did not correlate with mineral richness. A unimodal response of local species diversity to mineral richness (expressed as conductivity) was found. In the extremely mineral-rich, tufa-forming sites (conductivity > 600 μS cm−¹) a decrease in species diversity was encountered. Response curves of the most common species showed clear differentiation of their niches. Significant models of either unimodal or monotonic form were fitted for 18 of the 30 species analysed. Species showed five types of calcicole–calcifuge behaviour: (1) a decreasing monotonic response curve and a preference for the really acid sites; (2) a skewed unimodal response curve with the optimum shifted towards the slightly acid sites; (3) a symmetrical unimodal model response curve with the optimum in the base-rich sites, with no or slight tufa precipitation; (4) a skewed unimodal response curve but with the optimum shifted to the more mineral-rich sites; and (5) an increasingly monotonic response curve, the optimum in the extremely base-rich sites with strong tufa precipitation.
Main conclusions
Conductivity is the only reliable proxy measure of mineral richness across the entire gradient, within the confines of this study. This information is of great ecological significance in studies of fen mollusc communities. Species richness does not increase with increasing mineral richness along the entire gradient: only a few species are able to dwell in the extremely base-rich sites. The five types of calcicole–calcifuge behaviour seen in species living in fens have a wider application: data published so far suggest they are also applicable to mollusc communities in other habitats.
Aim The objectives were to (1) analyse the combined effects of soil pH, Ca content and soil moisture on total density and species richness of land snails in forest ecosystems, (2) explore relationships between the quantitative composition of snail assemblages and habitat characteristics, (3) investigate the relationships between soil pH and density of some of the most frequent species, and (4) compare the data with those from studies conducted in other temperate-humid regions of Europe.
Location Study sites were selected from 15 landscape types including different lithologies within the area of Baden-Württemberg (35,000 km2), SW Germany.
Methods Snails were recorded quantitatively from 83 study sites, with four plots representing a total of 0.25 m2 per site. Topsoil samples from each site were analysed for pH, exchangeable Ca, and Ca content of carbonates. Three categories of soil moisture (dry, intermediate and wet) were established and defined according to the (climatic) water balance. Numbers of individuals and species were brought in relation to soil moisture and soil pH. Cluster analyses were conducted to identify groups of quantitatively similar snail species assemblages.
Results Topsoil pH (2.7–7.5) and soil Ca contents were closely correlated. On dry soils, total snail density and species richness are generally low and do not change with pH, but clearly increase with increasing pH on intermediate moisture soils and on wet soils. On the latter, numbers of individuals and species are generally much higher compared with intermediate moisture sites at the same value of soil pH. Changes of density in relation to soil pH vary between species. Depending on the species, density increases only in the lower or only in the higher range of pH, is not related to pH, or decreases with increasing pH. Furthermore, these patterns vary within the same species depending on the region. This became evident from comparisons with other studies, particularly between sites in SW Germany and southern Scandinavia. From cluster analyses, subgroups of snail assemblages of high quantitative similarity were identified. Group formation is explained by soil pH to some extent, and one subgroup showed a connection with coniferous woodland sites on acidic soils. No further environmental factors available from our data could explain the clustering of snail assemblages more detailed.
Main conclusions Soil moisture is the strongest determinant of snail density and species richness at undisturbed woodland sites, but effects of soil moisture and soil pH on these patterns are closely interrelated on intermediate moisture soils and wet soils. However, the quantitative species composition of the land snail assemblages is related to soil properties to a lower degree than snail density and species richness, and other habitat characteristics such as vegetation or litter quality, can be important for species dominance in addition.